Kinetic studies on the reoxidation of beneficiated ilmenite by non-isothermal thermogravimetric analysis

Abstract

Synthetic rutile is an important titanium feedstock for the production of titanium dioxide pigment and titanium metal. More attention is focussed in recent years on the development of environment friendly processes for the production of synthetic rutile with minimum acidic effluents. CSIR-NIIST, Trivandrum, India, had successfully developed a more environment friendly process for the production of high grade synthetic rutile containing more than 94% TiO2. The process is comprised of metallisation of ilmenite followed by aeration rusting for the production of beneficiated ilmenite and the reoxdiation of beneficiated ilmenite followed by acid leaching. Reoxidation of beneficiated ilmenite plays a major role in rendering the product amenable to acid attack and removal of residual iron. This paper describes in detail the kinetic studies carried out on the reoxidation of beneficiated ilmenite by thermogravimetric technique under non-isothermal conditions. Assuming the oxidation mechanism to be in the form (1 - α)n and considering a contracting spherical model with n = 2/3, the basic equation of non-isothermal reaction was analysed and solved by integral approach. The kinetic parameters such as activation energy, pre-exponential factor and the order of the oxidation reaction were computed from the weight gain data under linear rise in temperature. The paper also discusses the optimisation of reoxidation temperature and residence time for the maximum removal of iron during acid leaching, which in turn results in synthetic rutile of maximum TiO2 content.